Updated on 11/6/2018.

This article will compare length of daylight hours at the Mars Science Laboratory at Gale Crater, Mars with high and low air and ground temperatures there. We will examine what was recorded for the solstices, the equinoxes, and the length of daylight on the warmest days and coldest nights. These days are color-highlighted on Table 1. To see the temperatures for dates not highlighted there, correlate the day lengh times on Table 1 with the following two links for this website:

Understanding where Mars is in its orbit. The solar longitude Ls is the Mars-Sun angle, measured from the Northern Hemisphere spring equinox where Ls=0. Ls=90 thus corresponds to summer solstice, just as Ls=180 marks the autumn equinox and Ls=270 the winter solstice (all relative to the northern hemisphere). In trying to understand where Mars is in its orbit, it’s important to know that while all Martian months involve a change of 30 degrees, there is a large variation in number of days in each of the 12 months there, and also a large variation in angular speed around the sun

While the slightly greater tilt of the Martian axis was not much of a factor around the equinoxes (Month 1, Sol 1; and Month 7, Sol 373), the tilt does make a significant difference at the solstices (Month 3, Sol 193; and Month 10, Sol 515). Note that aphelion (when Mars is furthest from the sun) and perihelion (when Mars is closest to the sun) does not correspond to the start of any Martian month. The next perihelion for Mars will be on October 28, 2016. On the Martian calendar this is Month 9, Sol 485, Ls 250.7. It will then be 1.38 AU from the sun. The last aphelion for Mars was on November 20, 2015 which on the Martian calendar is Month 3, Sol 151, Ls 70.6. It was 1.67 AU from the sun. The next aphelion will be on October 8, 2017.

TABLE 1: The following chart can be used to relate Martian Ls to hours and minutes of daylight at the latitude (4.59 South) of the Mars Science Laboratory rover Curiosity. The dates of solstices, equinoxes, aphelions, perihelions, record high and low temperatures are color highlighted.

TABLE 1 – DATA SUMMARIZING HOW LENGTH OF DAY LIGHT CORRELATED WITH TEMPERATURES AT MSL

Note: It generally takes 2 or 3 sols to move through each degree of Solar Longitude